The mean SEM is indicated around the graphs. 49, = 8 and = 8; week 10: control = 50, = 11 and = 7; week 11: control = 61, = 16 and = 8; week 12: control = 59, = 16 and = 7 and female mice: week 8: control = 37, = 10 and = 3; week 9: control = 49, = 18 and = 6; week 10: control = 50, = 23 and = 5; week 11: control = 56, = 27 and = 6; week 12: control = 54, = 26 and = 6. T Cell-Specific Loss of MALT1 Proteolytic Activity Causes Multi-Organ Inflammation After birth, mice were checked regularly and no external signs of suffering could be observed before the development of ataxia. However, upon sacrifice we noticed that the stomach of = 11, corresponding control mice: = 12; = 6, corresponding control mice: = 9. (D) Serum levels of IL-2, IL-4, IL-6, IL-17, IFN-, and TNF in = 10, corresponding control mice: = 11 and = 11, corresponding control mice: = 10. The mean SEM is indicated on the graphs. The statistical significance between groups 1-Methylpyrrolidine was calculated with an unpaired 2 tailed Student’s 1-Methylpyrrolidine < 0.05, **< 0.01, ***< 0.001, and ****< 0.0001. A T Cell-Intrinsic Role for MALT1 Proteolytic Activity Is Critical for Thymic nTreg Development The best known Tregs are Foxp3+CD25+CD4+ T cells (51), which have 1-Methylpyrrolidine two distinct developmental origins. Some develop in the thymus at a young agethe so-called natural Tregs (nTregs). Others mature in the periphery from na?ve conventional T cells during extended exposure to antigen or under inflammatory conditionsthe so-called induced Tregs (iTregs). Both populations are genetically distinct and have non-redundant functions (52, 53). MALT1 has been shown to be specifically required for thymic Treg development, while induced peripheral Treg formation in aged mice is not inhibited by MALT1 deficiency (4, 5, 54). The ability to induce Treg formation in differentiation studies using a high dose of anti-CD3 to stimulate the TCR (55). This might indicate a threshold effect which is influenced by MALT1. Therefore, we investigated the role of MALT1 proteolytic activity in thymic Treg development in young healthy (ataxia-free) (Figures 4D,E). This clearly indicates a T cell-intrinsic role for MALT1 protease activity in nTreg development. Open in a separate window Figure 4 Reduced Treg frequency and reduced surface CTLA-4 expression on Tregs and effector CD4+ T cells in = 6) (A) and = 3) (B) mice and their corresponding controls (= 5 and = 3, respectively). (C,D) Treg frequency in cLN of young = 6) (C) and = 3) (D) mice and their corresponding controls (= 5 and = 3, respectively). (E,F) Treg frequency in = 11) (E) and = 6) (F) mice suffering from ataxia and their corresponding controls (= 12 and = 9, respectively). Lymphocytes were stimulated for 4 h with PMA/ionomycin and the data represent three NARG1L individual experiments: experiment 1 = filled squares, experiment 2 = open squares and experiment 3 = open circles. (G,H) Normalized CTLA-4 expression on the surface of Tregs (G) and CD44+CD4+ T cells (H) 1-Methylpyrrolidine from young disease free = 15) and their corresponding controls (= 15). The individual percentages of Foxp3+CD4+ T cells or CD44+CD4+ T cells that express CTLA-4 on their surface is normalized against the average percentage of the corresponding control mice of each individual experiment. Lymphocytes were stimulated for 4 h with PMA/ionomycin and data represent two individual experiments: experiment 1 = filled.